The present invention relates to circular knitting machines and to methods of knitting circular or tubular fabric. More specifically, the present invention relates to circular knitting machines of the type having a rotatable cylinder carrying a plurality of needles and a knitting station with which are associated a plurality of yarn feed fingers independently movable into and out of respective yarn feeding positions for selectively feeding yarns to the needles, and relates further to methods of circular knitting practiced with such machines.
Circular knitting machines of the above-described type are normally provided with a relatively small diameter needle cylinder and only a single knitting station, and are conventionally used primarily for the knitting of socks and other hosiery, although such machines and the mechanisms and principles of operation thereof are clearly not so limited. Some of the varieties of types of hosiery produced on such machines include one or more pattern areas in which two or more differently colored yarns are knitted to form a distinctive pattern or design. Typically, such patterns or designs are utilized in the knitting of athletic socks and appear on the leg portion thereof. As will be appreciated by those skilled in the art, such pattern areas are conventionally formed by feeding a pattern yarn or yarns to and knitting such pattern yarn or yarns with only selected needles in the needle cylinder in the formation of each fabric course in the fabric pattern area while a background yarn is fed to and knitted by all of the cylinder needles in forming each such course whereby the pattern yarn appears only in the loops of each course of the pattern area of the fabric formed by the selected needles to which it is fed. The yarn feed fingers of most such machines are capable of feeding yarn to the needles at either a basic yarn feeding level spaced from an end of the needle cylinder or a pattern yarn feeding level spaced farther from the end of the cylinder, and therefore this feeding and knitting of the background and pattern yarns is conventionally accomplished in such machines by utilizing a feed finger capable of feeding yarn at the basic level for feeding the background yarn and utilizing a feed finger capable of feeding yarn at the pattern yarn feeding level for feeding the pattern yarn and by selectively positioning each of the cylinder needles for movement during cylinder rotation through the knitting station in axial projection from the end of the cylinder at either of two positions for receiving yarn from the feed fingers for knitting, the two positions being a basic position in which the needle projects from the cylinder to a sufficient extent to receive yarn fed at the basic level but will not receive yarn fed at the pattern yarn feeding level and an extended position in which the needle projects from the cylinder to a greater extent than in the basic position for receiving both yarn fed at the pattern yarn feeding level and yarn fed at the basic level.
Although this conventional arrangement on such machines operates effectively to form pattern areas, certain disadvantages exist in the use thereof. It is of primary importance in the formation of such pattern areas that the design formed by the pattern yarn be clearly defined and contrasted against the background area formed by the background yarn and, since both the background yarn and the pattern yarn are received and knitted by each selected needle knitting the pattern portion of the pattern area, it is necessary, to accomplish this, that the pattern yarn be of at least the same yarn count or denier as the background yarn. However, to provide continuity and a unitary appearance to the fabric, it is generally preferable that the pattern yarn be neither of a greater thickness than the background yarn or of a different type yarn. As a result, the problem of the background yarn "grinning" through, i.e. appearing in, the pattern portion of the pattern area is a recurring one in this type of knitting. Moreover, with this arrangement, the design portion of the pattern area is necessarily twice as bulky as the remaining portions of the fabric since both the pattern and background yarns are knitted therein, this resulting not only in an undesirable bulky and uneven appearance but also creating a strange feel to the hosiery fabric when worn.
In circular knitting machines of the type having a relatively large cylinder diameter and more than one knitting station, it is conventionally possible to knit pattern areas utilizing two knitting stations for separate feeding and knitting of the pattern and background yarns. Thus, for example, at one knitting station selected needles can be raised to a yarn receiving position, a pattern yarn fed thereto, and the selected needles manipulated to knit loops of such yarn all while the other cylinder needles are inactive, and, at the other knitting station, the other needles can be raised to the yarn receiving position, a background yarn fed thereto, and such other needles manipulated to knit loops of such background yarn while the needles which were active at the first knitting station are inactive. In this manner, neither the pattern yarn nor the background yarn is knitting in plating relationship with each other or with any other yarn, the background yarn floating behind loops of the pattern yarn and the pattern yarn floating behind loops of the background yarn. Importantly, this manner of knitting pattern areas is utilized almost exclusively for patterns which extend substantially around the entirety of the tubular fabric whereby both the pattern and background yarns are fully integrated in the fabric. Since the circular hosiery knitting machines of the type described above are conventionally provided with only a single knitting station, this manner of knitting pattern areas is not adaptable to such machines. Such hosiery machines, of necessity, must rely on the feeding of the pattern and background yarns at different levels and the positioning of the cylinder needles at different yarn receiving positions to achieve patterning and, due to the above-described conventional arrangement of the yarn feed fingers and needle positioning means of such hosiery machines, floating of the background yarn behind the pattern area is not conventionally possible. Moreover, the pattern portions of hosiery pattern areas conventionally knitted with such hosiery machines do not normally extend substantially around the entirety of the hosiery fabric knitted but instead appear at only one location thereon or are spaced at relatively substantial spacings around the tubular hosiery fabric, the pattern yarn normally being severed at the back of the hosiery fabric on opposite sides of the pattern. As a result, the manner of knitting pattern areas utilized by circular machines having more than one knitting station would not be feasible in knitting conventional hosiery patterns because the pattern and background portions of the hosiery would be separable.
Hosiery knit on this type of circular knitting machine additionally often include other types of special color effects, such as stripes, and in certain instances it is desirable that hosiery include both a pattern area and another type of color effect. One of the major limitations of conventional hosiery knitting machines in knitting such types of hosiery is the relatively limited capability of the main pattern drum and pattern chain assembly of the machine for diverse control of the yarn feed fingers thereof. Because the pattern drum is the sole means for controlling the movements of the yarn feed fingers into and out of their respective yarn feeding positions, it is necessary to utilize relatively large and cumbersome pattern drum and pattern chain arrangements to increase the capabilities of conventional machines for knitting such special color effects. In some cases, the size and complexity of the pattern drum and chain assembly necessary to knit hosiery with complex special color effects proves to be prohibitive.
In contrast to the above, the present invention provides an improvement in circular knitting machines of the type described and in the method of circular knitting utilizing same whereby, in knitting a pattern area, the background and pattern yarns may be selectively fed to and knitted by the needles at the basic and extended positions, respectively, so that the background yarn is not knitted by the needles knitting loops of pattern yarn but instead floats behind such loops in the knitted fabric and cannot grin through the pattern in the knitted fabric. Additionally, the present invention provides an independently operable means of controlling the movements of the yarn feed fingers in conjunction with the control thereof by the main pattern drum and thereby provides a means of significantly increasing the capacity of conventional hosiery knitting machines for knitting hosiery with complex striping and special color effects without increasing the size of the main pattern drum thereof and its associated pattern chain assembly.